Methods and systems for separating metals

ABSTRACT

Methods and systems for separating a first metal from a metal-containing feed stream are provided. The method can include applying solar energy, for example, by focusing one or more mirrors in one or more heliostats, to heat a metal-containing feed stream in a heating zone to a first temperature to produce a first vapor including the first metal. The first vapor can be condensed in a condensation zone to produce a first liquid including the first metal, and the first liquid can be collected. The system can include a separation unit include a heating zone in fluid communication with a condensation zone and a means for applying solar energy to heat a metal-containing feed stream disposed in the heating zone.

CROSS-REFERENCE TO RELATED APPLICATIONS

This patent application is a divisional of U.S. patent application Ser.No. 17/185,338 filed on 25 Feb. 2021, which claims the benefit of U.S.Provisional Patent Application No. 62/985,009, filed on 4 Mar. 2020. Theentire disclosures of each of the above recited applications areincorporated herein by reference.

FIELD

Methods and systems are provided herein for separating metals from ametal-containing feed stream using solar energy, for example, using oneor more heliostat.

BACKGROUND

The background description includes information that may be useful inunderstanding the systems and methods described herein. It is not anadmission that any of the information provided herein is prior art, orthat any publication specifically or implicitly referenced is prior art.

Metals extracted from the earth traditionally require further refiningto remove impurities to arrive at high purity metals, which can be usedin various industrial applications. Metals can also be present invarious waste streams, such as mining waste streams and industrial wastestreams. Thus, the recovery of metals from such waste streams isdesirable so the recovered metals can be used in other applications. Onemethod for separation and/or purification of metals is a distillationprocess. Distillation of metals involves heating a metal-containingstream to a temperature suitable to vaporize the metal to be separatedfollowed by condensing the vaporized metal in order to recover themetal. During distillation, impurities, such as lower volatility metals,can remain in the metal-containing stream.

U.S. Pat. No. 2,239,371 reports a method and apparatus for separation ofmetals by distillation, particularly, separation of lead, arsenic,antimony, bismuth, and tin.

U.S. Pat. No. 2,607,675 reports a method for distillation of metals,particularly separation of non-volatile metals.

A significant amount of energy can be required to heat ametal-containing feed during distillation to vaporize a metal and moreenergy can be required if the metal to be separated has a higher heat ofevaporation and a lower vapor pressure. The energy needed duringdistillation can be generated by combusting fossil fuels, for example,burning coal to produce electricity. This combustion of fossil fuels canemit a substantial amount of CO₂. Therefore, improved processes fordistilling metals are needed which require less energy and emit lessCO₂.

SUMMARY

This section provides a general summary of the disclosure, and is not acomprehensive disclosure of its full scope or all of its features.

The present disclosure relates to methods and systems for separatingmetals from a metal-containing feed stream. In various aspects, thepresent disclosure provides a method for separating a first metal from ametal-containing feed stream. The method includes applying solar energyto heat the metal-containing feed stream in a heating zone to a firsttemperature to produce a first vapor including the first metal. Themethod further includes condensing the first vapor in a condensationzone to produce a first liquid including the first metal and collectingthe first liquid.

In various aspects, the present disclosure also provides a system forseparating a first metal from a metal-containing feed stream. The systemincludes a separation unit including a heating zone and a condensationzone, wherein the heating zone is in fluid communication with thecondensation zone. The system also includes a means for applying solarenergy to heat the heating zone and a metal-containing feed streamdisposed inside the separation unit.

In various aspects, the present disclosure provides a method forseparating a low volatility metal from a metal-containing feed stream.The method includes applying solar energy to heat the metal-containingfeed stream in the presence of a halide of a volatile metal in a heatingzone to a first temperature to produce a first vapor mixture including alow volatility metal halide and the volatile metal. The method furtherincludes converting the first vapor mixture into the low volatilitymetal and the halide of the volatile metal and condensing the lowvolatility metal to produce a first liquid including the low volatilitymetal. The first liquid may be collected.

Various objects, features, aspects and advantages of the present subjectmatter will become more apparent from the following detailed descriptionof preferred embodiments.

DETAILED DESCRIPTION

I. Methods of Separating Metals

Methods of separating a first metal from a metal-containing feed streamare provided herein. The methods can include heating themetal-containing feed stream in a heating zone to a first temperature toproduce a first vapor comprising the first metal. For example, themetal-containing feed stream can be flowed over a surface heated to atemperature, e.g., a first temperature, capable of vaporizing the firstmetal to produce the first vapor. In any embodiment, themetal-containing feed stream can be in a liquid state, e.g., a moltenstate, or a solid state, e.g., as a powder, as granule, or asbriquettes. The first temperature can be determined by a person ofordinary skill in the art based on upon the composition of themetal-containing feed stream, the first metal to be separated, and theconditions for separation (e.g. pressure at which the metal-containingfeed stream is heated). For example, the first temperature can begreater than or equal to a temperature at which the first metal iscapable of vaporizing at a specified pressure. In some embodiments, thefirst temperature may be greater than or equal to the boiling point ofthe first metal. In some embodiments, the first temperature can begreater than or equal to about 250° C., greater than or equal to about500° C., greater than or equal to about 750° C., greater than or equalto about 1,000° C., greater than or equal to about 1,250° C., greaterthan or equal to about 1,500° C., greater than or equal to about 1,750°C., greater than or equal to about 2,000° C., greater than or equal toabout 2,250° C., greater than or equal to about 2,500° C., greater thanor equal to about 2,750° C., greater than or equal to about 3,000° C.,greater than or equal to about 3,250° C., greater than or equal to about3,500° C., greater than or equal to about 3,750° C., or greater than orequal to about 4,000° C.; or from about 250° C. to about 4,000° C.,about 750° C. to about 4,000° C., about 1000° C. to about 4,000° C., orabout 2,000° C. to about 4,000° C.

In some embodiments, the metal-containing feed stream can be heated inthe heating zone at a pressure below atmospheric pressure. In otherwords, at least a portion of the separation process may be performedunder a vacuum. In such embodiments, the first temperature can be lessthan the boiling point of the first metal. In some embodiments, thepressure under which the metal-containing feed stream is heated can beless than or equal to about 100,000 Pa, less than or equal to about50,000 Pa, less than or equal to about 10,000 Pa, less than or equal toabout 1,000 Pa, less than or equal to about 100 Pa, less than or equalto about 20 Pa, or about 1 Pa; or from about 1 Pa to about 50,000 Pa,about 1 Pa to about 10,000 Pa, about 1 Pa to about 1,000 Pa, about 1 Pato about 100 Pa or about 1 Pa to about 20 Pa.

The methods further include cooling or condensing the first vapor in acondensation zone to produce a first liquid comprising the first metal.For example, the first vapor can be flowed over a cooled surface, e.g.,in a condenser, at a second temperature, which is capable of condensingthe first metal in the first vapor to produce the first liquid. Thefirst liquid may form on the cooled surface. The second temperature canbe determined by a person of ordinary skill in the art based on upon thefirst metal vapor to be condensed and the conditions for condensing(e.g. pressure at which the first metal vapor is cool). For example, thesecond temperature can be greater than or equal to the melting point ofthe first metal and/or less than the boiling point of the first metal.In some embodiments, the second temperature can be less than or equal toabout 4,000° C., less than or equal to about 3,750° C., less than orequal to about 3,500° C., less than or equal to about 3,250° C., lessthan or equal to about 3,000° C., less than or equal to about 2,750° C.less than or equal to about 2,500° C., less than or equal to about2,250° C., less than or equal to about 2,000° C., less than or equal toabout 1,750° C., less than or equal to about 1,500° C., less than orequal to about 1,250° C., less than or equal to about 1,000° C., lessthan or equal to about 750° C., less than or equal to about 500° C.,less than or equal to about 250° C., or less than or equal to about 100°C.; or from about 100° C. to about 4,000° C., about 250° C. to about3,000° C., about 500° C. to about 2,000° C., or about 1250° C. to about2,000° C. The first liquid may be collected to recover the first metal.Optionally, the first liquid may be solidified via further cooling.

In any embodiment, the metal-containing feed stream can also comprise atleast one further metal in addition to the first metal, e.g. a secondmetal, a third metal, a fourth metal, etc., as well as mixtures oralloys of metals. In some aspects, a further metal may be considered tobe an impurity or it may be another metal to be recovered through theseparation process. Additionally or alternatively, the metal-containingfeed stream may also include non-metal impurities, for example, carbon,hydrogen, oxides, carbides, etc. In any embodiment, a second metal, anon-metal impurity or a combination thereof may not substantiallyvaporize at the first temperature during the separation method therebyremaining in the metal-containing feed stream. The metal-containing feedstream may be derived from any metal-containing stream comprising thefirst metal. For example, the metal-containing feed stream can bederived from a metal mining stream, black sands, a waste streamcomprising the first metal, or combinations thereof.

In any embodiment, the first metal and further metal (e.g. a secondmetal, a third metal, a fourth metal, etc.) may each be independentlyselected from the group consisting of an alkali metal (e.g., Na, K, Rb),an alkaline earth metal (e.g., Be, Mg, Ca, Sr), a transition metal(e.g., Ti, Zr, V, Nb, Ta, Mo, W, Re, Fe, Ru, Os, Co, Rh, Ir, Ni, Pd, Pt,Cu, Ag, Au, Zn, Hg), a basic metal (e.g., Al, Ga, In), and a semi metal(e.g., Si, Ge, As, Sb). In some embodiments, the first metal may be Ptor Pd.

In any embodiment, a metal-containing feed stream as described hereincan be heated via solar energy in a heating zone to a suitabletemperature, e.g., a first temperature, to produce a first vaporcomprising the first metal. Advantageously, the use of solar energy canresult in lower CO₂ emission during the metal separation method.Sunlight can provide heat to the heating zone using various solarheating devices as known in the art. For example, mirrors to reflectsunlight onto the heating zone may be used, such as a parabolic mirror.In any embodiment, one or more heliostats having one or more mirrors maybe used to reflect sunlight to heat a metal-containing feed stream in aheating zone to a first temperature to produce a first vapor comprisingthe first metal. In various aspects, the one or more mirrors in the oneor more heliostats can be arranged to reflect sunlight to a focalvertex. The heating zone containing the metal-containing feed stream maybe disposed in proximity to the focal vertex such that themetal-containing feed stream is heated to a suitable temperature, e.g.,a first temperature, to vaporize the first metal. In some embodiments,multiple heliostats may be arranged in array or a tower to reflectsunlight and provide solar energy for heating the metal-containing feedstream. Alternatively, a solar oven may be used to heat ametal-containing feed stream. It is also contemplated herein that thesolar energy as described above may be used to supply energy for othersteps of the methods described herein. For example, solar energy may beused to condense or cool the first liquid and/or solar energy may beused to solidify the first liquid, and/or solar energy may be used tomaintain the metal-containing feed stream in a liquid state.

Additionally or alternatively, energy required for the methods describedherein, for example, heating the metal-containing feed stream, coolingthe first vapor, solidifying the first liquid, etc., may be supplied byvia a wireless power routing system as described in U.S. Pat. No.10,418,842, which is incorporated herein by reference in its entirety.

In further embodiments, methods are provide herein for separating a lowvolatility metal from a metal-containing feed stream. For example, thefirst metal may be a low volatility metal with a lower vapor pressureand high heat of evaporation. The method can include selecting a halideof a volatile material (also referred to as a “volatile materialhalide”). The volatile material can be any volatile element, preferablya volatile metal. A halide of a volatile metal is also referred to as a“volatile metal halide.”

The vapor of the volatile material halide (e.g., volatile metal halide)can be selected to have an average heat of dissociation into volatilematerial atoms vapor (e.g., volatile metal atoms vapor) and halogenatoms: (i) smaller than the average heat of dissociation of the vapor ofa halide of a low volatility metal (also referred to as a “lowvolatility metal halide”) into halogen atoms and low volatile metalatoms; and (ii) greater than the average heat of dissociation of thevapor of the low volatility metal halide into halogen atoms andcondensed low volatility metal, as described in U.S. Pat. No. 2,607,675,which is herein incorporated by reference in its entirety. The averageheat of dissociation of the vapor of the volatile material halide (e.g.,volatile metal halide) into volatile material atoms vapor (e.g.,volatile metal atoms vapor) and halogen atoms is the heat ofdissociation of volatile material halide (e.g., volatile metal halide)into the vapor of the volatile material atoms (e.g., volatile metalatoms vapor) and the halogen atoms formed by the dissociation divided bythe number of those halogen atoms. The volatile material halide (e.g.,volatile metal halide) may be a lower halide or a higher halide,preferable a higher halide. The average heat of dissociation of thevapor of the low volatility metal halide into halogen atoms and lowvolatility metal atoms or condensed low volatility metal, respectively,is the total heat of dissociation of the low volatility metal halideinto halogen atoms and low volatility metal atoms or condensed lowvolatility metal, respectively, divided by the valency of the lowvolatility metal in the low volatility metal halide.

In some embodiments, the volatile material halide (e.g., volatile metalhalide) must not form with the low volatility metal, or with anyconstituent of the metal-containing feed stream, any non-volatilecombination (compound, alloy, solution) (or any stable, though volatile,compounds) which would prevent recovery of the low volatility metal byreversal of the reaction. For instance, if a phosphorus halide is usedin the method as a volatile material halide, none of the metalscontained in the metal-containing feed stream can form nonvolatilephosphides which are stable under the conditions of reaction.Additionally or alternatively, under the conditions of the reaction andin contact with the metal-containing feed stream, the stable halide ofthe low volatility metal cannot be converted into an unstable lowerhalide of the low volatility metal to any noticeable extent.

Thus, the method can include separating a low volatility metal from ametal-containing feed stream by applying solar energy as described aboveto heat the metal-containing feed stream in the presence of a volatilemetal halide in a heating zone to a first temperature as described aboveto produce a first vapor mixture. In some embodiments, the firsttemperature can be less than a temperature required to vaporize the lowvolatility metal (e.g., the boiling point of the low volatility metal)and/or greater than a temperature required to vaporize the volatilemetal (e.g., the boiling point of the volatile metal) of the volatilemetal halide. The heating of the metal-containing feed stream can beperformed at a pressure as described above, for example, at pressurelower than atmospheric pressure. In various aspects, the volatile metalhalide can be in vapor form when contacted with the metal-containingfeed stream in the heating zone.

As further illustrated below, the following reaction can take placeduring heating of the metal-containing feed stream in the heating zone:mM¹(c)+nM²X_(m)(v)↔nM¹X_(n)(v)+nM²(v)  (I)where M¹(c) represents the condensed (e.g., solid or liquid) lowvolatility metal to be separated, which is assumed to have a valency n,if X represents a halogen and if M²X_(m)(v) represents the vapor of thevolatile metal halide. M¹X_(n)(v) and M²(v) represent the vapor of thelow volatility halide and the vapor of the volatile metal or metalloid,respectively. For example, if beryllium is the low volatility metal tobe separated and sodium chloride is the volatile metal halide, thereaction is as follows:Be(c)+2NaCl(v)↔BeCl₂(v)+2Na(v).Thus, the first vapor mixture produced can include: (i) a low volatilitymetal halide formed from an exchange reaction with the low volatilitymetal and the volatile metal halide; and (ii) the volatile metal fromthe volatile metal halide.

In some embodiments, if the low volatility metal to be separated has avalency n and is represented as M¹(c) and if a higher halide (M³X_(f))of a metal (M³), which is as volatile as its lower halide (M³X_(g))(g<f) the reaction is as follows:(f−g)M¹(c)+nM³X_(f)(v)↔(f−g)M¹X_(n)(v)+nM³X_(g)(v)  (II).For example, if aluminum trichloride is the (stable) higher halide andaluminum monochloride is the (unstable) lower halide, the reaction is asfollows:2M¹(c)+nAlCl₃(v)↔2M¹Cl_(n)(v)+nAlCl(v).

Additionally, the method can include converting the first vapor mixtureinto the low volatility metal and the volatile metal halide. Forexample, the first vapor mixture may be cooled to a suitable temperaturewherein the volatile metal vapor reacts with the low volatility metalhalide vapor and forms the low volatility metal (“converted lowvolatility metal”) and the volatile metal halide. The converted lowvolatility metal can then be condensed or cooled at a suitabletemperature to produce a first liquid comprising the low volatilitymetal. The first liquid may be collected to recover the low volatilitymetal. Optionally, the first liquid may be solidified via furthercooling.

In any embodiment, the low volatility metal can be selected from thegroup consisting of beryllium, vanadium, rhenium, tantalum, niobium,tungsten, molybdenum, nickel, cobalt, iron, ruthenium, rhodium,palladium, silver, osmium, iridium, platinum, and copper. In someembodiments, the low volatility metal may be platinum or palladium.

The volatile metal halide can be selected from a group consisting of analkali metal halide, an alkaline earth metal halide, a basic metalhalide, arsenic halide, cadmium halide, mercury halide, thallium halide,zinc halide, tin halide, lead halide, and combinations thereof. Thus,the volatile metal can be selected from the group consisting of analkali metal, an alkaline earth metal, a basic metal, arsenic, cadmium,mercury, thallium, zinc, tin, and lead. In any embodiment, the halidecan be selected from the group consisting of a chloride, a fluoride, abromide, or an iodide, preferably a fluoride or a chloride. In someembodiments, the volatile metal halide can be sodium chloride oraluminum trichloride.

II. Systems for Separating Metals

Systems for separating metals are also provided herein. The system mayinclude a separation unit including a heating zone and a condensationzone, wherein the heating zone is in fluid communication with thecondensation zone. The system can further include a means for applyingsolar energy to heat the heating zone and a metal-containing feed streamas described herein disposed inside the separation unit, particularly,in the heating zone.

Any suitable means for applying solar energy to heat themetal-containing feed stream in the heating zone to a suitabletemperature, e.g., a first temperature, to produce a first vaporcomprising the first metal may be used. For example, mirrors to reflectsunlight onto the heating zone may be used, such as a parabolic mirror.A solar oven may also be used. Additionally or alternatively, the meansfor applying solar energy may include one or more mirrors organized intoone or more heliostats. The one or more mirrors may be arranged orarrayed to reflect sunlight to a focal vertex, and the heating zone maybe disposed near or at the focal vertex. In any embodiment, the focalvertex is disposed at least about 5 meters, at least about 10 meters, atleast about 25 meters, at least about 50 meters, at least about 75meters, or about 100 meters above the top of the tallest mirror.

The term ‘about’, unless otherwise indicated, when used in conjunctionwith a numeral refers to a range spanning +/−10%, inclusive, around thatnumeral. For example, the term ‘about 10 μm refers to a range of 9 to 11μm, inclusive.

The recitation of ranges of values herein is merely intended to serve asa shorthand method of referring individually to each separate valuefalling within the range. Unless otherwise indicated herein, eachindividual value is incorporated into the specification as if it wereindividually recited herein. All methods described herein can beperformed in any suitable order unless otherwise indicated herein orotherwise clearly contradicted by context.

The use of any and all examples, or exemplary language (e.g. “such as”)provided with respect to certain embodiments herein is intended merelyto better illuminate the invention and is not intended to pose alimitation on the embodiments disclosed herein. No language in thespecification should be construed as indicating any non-claimed elementessential to the practice of the invention.

It should be apparent to those skilled in the art that many moremodifications besides those already described are possible. The systems,methods and devices disclosed herein are not to be restricted except inthe scope of the appended claims. Moreover, in interpreting both thespecification and the claims, all terms should be interpreted in thebroadest possible manner consistent with the context. In particular, theterms “comprises” and “comprising” should be interpreted as referring toelements, components, or steps in a non-exclusive manner, indicatingthat the referenced elements, components, or steps may be present, orutilized, or combined with other elements, components, or steps that arenot expressly referenced. Where the specification claims refers to atleast one of something selected from the group consisting of A, B, C . .. . and N, the text should be interpreted as requiring only one elementfrom the group, not A plus N, or B plus N, etc.

What is claimed is:
 1. A method for separating a low volatility metalfrom a metal-containing feed stream, the method comprising: applyingsolar energy to heat the metal-containing feed stream in the presence ofa volatile metal halide in a heating zone to a first temperature toproduce a first vapor mixture comprising a low volatility metal halideand a volatile metal, wherein the metal-containing feed stream isderived from black sands; converting the first vapor mixture into thelow volatility metal and the volatile metal halide; condensing the lowvolatility metal to produce a first liquid comprising the low volatilitymetal; and collecting the first liquid.
 2. The method of claim 1,wherein the metal-containing feed stream is heated at a pressure belowatmospheric pressure.
 3. The method of claim 1, wherein themetal-containing feed stream is in a solid or a liquid state.
 4. Themethod of claim 1, further comprising solidifying the first liquid. 5.The method of claim 1, wherein the low volatility metal is selected fromthe group consisting of beryllium, vanadium, rhenium, tantalum, niobium,tungsten, molybdenum, nickel, cobalt, iron, ruthenium, rhodium,palladium, silver, osmium, iridium, platinum, and copper; and thevolatile metal is selected from the group consisting of an alkali metal,an alkaline earth metal, arsenic, cadmium, mercury, thallium, zinc, tin,and lead.
 6. The method of claim 1, wherein the halide is selected fromthe group consisting of a chloride, a fluoride, a bromide, or an iodide.7. The method of claim 1, wherein the solar energy is applied byfocusing one or more mirrors in one or more heliostats.
 8. The method ofclaim 7, wherein the heliostats are arranged in an array or a tower toreflect sunlight and provide solar energy for heating themetal-containing feed stream.
 9. The method of claim 7, wherein the oneor more mirrors in the one or more heliostats reflect sunlight to afocal vertex and the heating zone is disposed at the focal vertex.